Dual-functional additive of cesium ion for achieving ultrahigh efficiency of persistent phosphorescence in existing polymer-based materials

Despite great achievements obtained for polymer-based room-temperature phosphorescence (RTP) materials, the limited efficiencies of persistent RTP still hinder their development. Herein, a simple and universal strategy of using the dual-functional additive of Cs⁺ was presented, which could simultaneously enhance the efficiency (Φ_p) and maintain the long lifetime (τ_p) of RTP in existing polymer-based systems with various phosphors and polymers. Among them, the commercial emitter (TpB)-doped polyvinyl alcohol (PVA)/Cs₂CO₃ system possessed an extremely high Φ_p up to 75.5% and still maintained a long τ_p of 2.13 s, by introducing the heavy-atom effect and an extra network of ionic bonding through the Cs⁺ additive. Additionally, the temperature resistance of RTP in TpB@PVA/Cs⁺ film could also be improved to 85 °C. More satisfactorily, the efficiency of Förster resonance energy transfer (FRET) from RTP to near-infrared (NIR) was also remarkably enhanced in the multi-component systems. This work provides a simple and universal strategy for developing polymer systems with high RTP performance.